The main reason I don't use step up rings to standardize my filters to one size is because I value lens hoods. You simply cannot use the proper lens hood when you use a nonstandard size filter. Just something to keep in mind.

If you want a polarizer, I recommend a Nikon branded one. I have one and it's actually less expensive than many other premium brands. Quality seems to be top notch as well. On top of it, it comes in a nice carrying case. I like mine.

The main reason I don't use step up rings to standardize my filters to one size is because I value lens hoods. You simply cannot use the proper lens hood when you use a nonstandard size filter. Just something to keep in mind.

I do this all the time. My filters are 77mm. Other than 52mm lenses which are way too small, all other sizes (that I have) actually fits the filter and the ring inside the hood. It's not an easiest thing to install nor adjust (polarizers) but the fact is, in many cases, you actually can....

All of my lenses have a hood bayonet on the leading edge of the lens barrel.

All filters degrade the image to a certain extent. A filter adds two additional surfaces into the light path. This is one aspect of photography where it pays to buy the very best. Ansel Adams recommends using filters conservatively. Over the years I have bought many filters only to find that I seldom use them. The one that is used most (and this is only ocassionally) is a medium yellow filter to darken the sky. This filter approximates what the human eye sees when using panchromatic films.

A rock pile ceases to be a rock pile the moment a single man contemplates it, bearing within him the image of a cathedral.